The invention relates generally to an optical device for measuring the depth of a surface at a selected point and more specifically concerns an optical device for measuring the contour of a surface.
The prior art utilizes basically two types of devices for measuring the contour of a surface. They are mechanical depth gage devices and optical stereographic devices. The mechanical depth gage devices uses a probe which has graduated markings that are placed into contact with the surface, and the distance from some reference point is read. The probe is then moved about to take the number of measurements appropriate to the completeness of the data required. The optical stereographic devices use the principle of change of perspective with angle at a known distance to determine depth by geometry. Here again particular points are selected and geometry is employed until all necessary data is obtained.
The disadvantages of these prior art devices are the laborious point-to-point measurements necessary with the optical stereographic devices and the surface contacting that must be employed in the mechanical depth gage devices.
In another related type of device the principle of optical defocus is used to measure the roughness of a surface. An example of this type of device is disclosed in U.S. Pat. No. 3,734,626. This type of device could possibly be used to measure the contour of a surface; however, for such use it would be subjected to errors due to changes in reflectivity or slope of the surface.
It is therefore the primary purpose of this invention to provide a device for measuring the contour of a surface that is not subjected to errors due to the changes in reflectivity or slope of the surface.
It is another object of this invention to provide a device for measuring the depth of a surface without resorting to any motion of a depth determining senor.
A further object of this invention is to provide a device for measuring the depth of a surface without making actual contact with the surface.
Still another object of the invention is to provide a device for measuring the depth of a surface without having to make point-to-point measurements.
Other objects and advantages of this invention will become apparent in the following specification and drawing.